DA TA SHEET AA T362052ebad10ee97eea25d5e-d7d40819259e7d3022d9ad53e… · · 2013-03-285 EN In Charge enable input, active high, with internal pull-up ... IN = 5.5V, T A = -25°C

AAT3620 DATA SHEET

Single Cell Li+ Switch Mode Battery Charger

1Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com

201904C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 11, 2012

Typical Application

22µF

BATT-

TEMP

BatteryPack

VPIN

EN

TS

LX

BATT+

Adapter

10µF

CS

BAT

PGND

STAT2

STAT1

CT

4.7µH

GND

Charge Enable

Timer Disable

Charging Status 1Charging Status 2

ISET

ITERM Termination Current Set& Charge Current Indicator

Charge Current Set

0.1µF

VCC

0.1µF

VCC

100Ω

1µF

AAT3620

RT1

RT2

RTERMRSET

General DescriptionThe BatteryManager™ AAT3620 is an ideal solution for charging high capacity Li+ batteries. The AAT3620 can supply up to 2.0A charge current with minimal thermal impact to mobile systems with features such as color display, camera with flash, organizer, video, etc, that require battery capacity to keep pace with the power requirements.

The AAT3620 is a PWM switch mode/linear charger with high charge efficiency at the full constant current (fast charge) rate. Based on a 1.5MHz PWM step-down “buck” converter, the AAT3620 PWM switch mode controls the constant current charge mode up to 2.0A, and auto-matically switches to linear mode charging during the battery conditioning low level current and the light load end of charge current termination region. The full charge rate and the end of charge current can be programmed with separate external resistors. A shared charge current indication pin is available for a Coulomb counter.

Battery charge temperature and charge state are fully monitored for fault conditions. In the event of an over-current, over-voltage, short-circuit or over-temperature failure, the device will automatically shut down. Two status monitor output pins are provided to indicate the battery charge status and power source status though two display LEDs. The AAT3620 has a no-battery detec-tion feature, "No-BAT", which requires the safety timer. The AAT3620-2 option is for applications where the safety timer may be disabled independently and the "No-BAT" feature is not required.

The AAT3620 is available in a thermally enhanced, space-saving 14-pin 3mm x 3mm TDFN package.

Features• 4.3V~6.0VInputRange• Upto2.0AChargeCurrentCapability• 1.5MHzPWM/LinearCharger• Over90%FullRateChargeEfficiency• IntegratedSwitchingDevice• "No-BAT"Detect–AAT3620Only• SafetyTimer• IntegratedSenseResistor• Built-inReverseBlockingFeature• BatteryPreconditioning/ConstantVoltage/Constant

Current Charge Mode• ProgrammableEndofChargeCurrent• 1%ConstantVoltageModeRegulation• Built-inProgrammableChargingTimer• ChargeCurrentIndicationPin• Over-Voltage,Over-Current,andOver-Temperature

Protection• BatteryOver-TemperatureProtection• Power-OnResetandSoft-Start• TDFN33-14Package

Applications• DigitalCamcorders• PointofService(POS)• PortableDVDPlayers• PortableHand-heldSolutions• PortableMediaPlayer

AAT3620 DATA SHEET




Pin Description

Pin# Name Type Function1 VPIN In Adapter power input.2 PGND Ground Power ground.3 GND Ground Analog ground connection.4 VCC In SupplyInput.5 EN In Chargeenableinput,activehigh,withinternalpull-up(toVPIN).6 ISET In ConnectRSETresistortopintosetconstantcurrentchargecurrent.

7 CT In/Out Timerpin:connecttimingcapacitorhereforchargetimerfunction(AAT3620-2ONLY);con-nect to ground to disable the timer function.

8 STAT2 Out Battery charge status 2 indicator pin to drive an LED, open-drain.9 STAT1 Out Battery charge status 1 indicator pin to drive an LED, open-drain.

10 TERM In/Out ConnectRTERMresistortopintosetterminationcurrent.Chargingcurrentcanbemonitorwiththispin.LeaveOPENtosetto200mAdefaultterminationcurrent.

11 TS In/Out Batterypacktemperaturesensinginput.TodisableTSfunction,pulluptoVCC through 10k resistor.

12 BAT Out Battery positive terminal connecting pin.13 CS In Returnpinforinductorforinternalcurrentsensing14 LX In/Out Switchingnode.

EP EP GroundThe exposed thermal pad (EP) must be connected to board ground plane and pins 2 and 3. The ground plane should include a large exposed copper pad under the package for thermal dissipation (see package outline).

Pin Configuration

TDFN33-14 (Top View)

VPINPGND

GND

1

VCCEN

ISET

LX

EP

CSBATTSTERMSTAT1

2

3

4

5

6

CT 7

12

11

14

13

10

9

STAT28

AAT3620 DATA SHEET




Absolute Maximum Ratings1

Symbol Description Value UnitsVP VPIN,LX -0.3 to 6.5

VVN Otherpins -0.3toVP + 0.3TJ OperatingJunctionTemperatureRange -40 to 150 °CPD Maximum Power Dissipation 2.5 W

TLEAD MaximumSolderingTemperature(atLeads) 300 °C

Thermal Information

Symbol Description Value UnitsqJA MaximumThermalResistance(3x3mmTDFN-14)2 50 °C/WPD Maximum Power Dissipation3 2 W

1.StressesabovethoselistedinAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.Functionaloperationatconditionsotherthantheoperatingconditionsspecified is not implied.

2.MountedonanFR4board.3. Derate 2.7mW/°C above 25°C ambient temperature.

AAT3620 DATA SHEET




Electrical Characteristics1

VIN=5.5V,TA=-25°Cto85°C;unlessotherwisenoted,typicalvaluesareatTA = 25°C.

Symbol Description Conditions Min Typ Max UnitsOperation

VIN AdapterInputVoltage 4.3 6.0V

VCC_UVLO InputUnder-VoltageLockoutVPINRising 3.5 4.3Hysteresis 150 mV

VVIN_SLEEP InputSleepVoltage NoChargeifVVIN<VVIN_SLEEP VBAT + 0.05 VBAT + 0.2 V

IVIN_OP OperatingSupplyCurrent EN = High, Charge Current = 200mA 5mA

IVIN_STBY StandbySupplyCurrent EN=High,NoCharge,Power-SaveMode 2

IVIN_SHDN ShutdownSupplyCurrent EN=Low,LXFloating,SleepMode 10

µAIFWD_LKG

Forward Leakage Current, Mea-sured from LX to Ground EN=Low,LX=5.5V 1

IREV_LKGReverseLeakageCurrent,Mea-suredfromLXtoVIN

EN=LoworHigh,VIN=0V, LX=5.5V 1

IBAT_LKG Bat Pin Leakage Current VBAT=4.2V,VIN=0Voropen 1

RDS(ON)InternalPMOSOnResistance VIN=5.5V 170 300

mΩInternalNMOSOnResistance VIN=5.5V 120 250

fSW PWMSwitchingFrequency VBAT=3.6V,ICH_CC = 1A 1.2 1.5 1.8 MHzCharge RegulationVBAT_REG OutputChargeVoltageRegulation 4.158 4.20 4.242 V

tSOFT_START ChargingSoft-StartDelay DelayofChargefromEN,orVCC_UVLO, orVVIN_ADPP

100 us

VBAT_BCBatteryConditioningBatteryVolt-age Threshold

Preconditioning Battery Charge when VBATrising:VBAT<VBAT_BC

2.4 2.6 2.8 V

ICH_BCBattery Conditioning Charge Cur-rent WhenVBAT<VBAT_BC 0.1∙ICH_ CC A

ICH_BC_TYPTypical Battery Conditioning Charge CurrentSettingRange 100 200 mA

tCH_BC BatteryConditioningTimeOut StopChargeifPreconditioningTimeis more than tCH_BC

-15% 0.25∙CCT +15% Minute/nF

ICH_CCConstant-Current Battery Charge Current Accuracy

WhenVBAT_BC<VBAT<VBAT_REG, 1A to 2A -15% ICH_CC +15 %

tCH_CCTOFast Constant Current Charge Time Out

StopChargeifFastChargeTimeismore than tCH_CCFAST

-15% 0.022∙CCT +15%Hour/nF

tCH_CVTO ConstantVoltageChargeTimeOut StopChargeifChargeTimeismorethan tCH_CV

-15% 0.03∙CCT +15%

VBAT_RCH BatteryRechargeVoltageThreshold IfVBATFallsBelowVBAT_RCH,RechargeStarts VBAT_REG - 0.1 V

ICH_TERM_TYP

Charge Termination Threshold Cur-rent

TerminateCVChargeif ICH < ICH_TERM

RTERM∙10-6 A

ICH_TERM_RANGE

Typical Termination Threshold Cur-rentSettingRange

Charger Termination Current will be Clamped to the Minimum or Maxi-mumValueifSetAboveorBelowtheITERMRange.

50 200 mA

1.Specificationoverthe–25°Cto+85°Coperatingtemperaturerangeisassuredbydesign,characterizationandcorrelationwithstatisticalprocesscontrols.

AAT3620 DATA SHEET




Electrical Characteristics1

VIN=5.5V,TA=-25°Cto85°C;unlessotherwisenoted,typicalvaluesareatTA = 25°C.

Symbol Description Conditions Min Typ Max UnitsLogic and Status Input/Output

VIH EN Input Low Threshold 1.6V

VIL EN Input Low Threshold 0.4

IEN ENPinSupplyCurrentEN=VIN 0.1 1

µAEN=0V 0.6 10ISLEAK STAT1,STAT2PinLeakageCurrent When output FET is off 1ISTATx STAT1andSTAT2PinCurrentSinkCapability 10 mA

tSTAT_PULSE STATPulseWidth In fault conditions: CCT = 100nF 0.5 sfSTAT_FLASH STATPulseFrequency In fault conditions: CCT = 100nF 1 HzProtectionVBAT_OVP BatteryOver-VoltageProtectionThreshold NochargeifVBAT>VBAT_OVP VBAT_REG + 0.2 V

ICL Over-CurrentProtectionThresholdandLimit 2.46 3.0 4.0 A

VTS1 TSHotTemperatureFaultThresholdVTS falling 29.1 30 30.9 %VHysteresis 50 mV

VTS2 TSColdTemperatureFaultThresholdThresholdVTS rising 58.2 60 61.8 %VHysteresis 50 mV

TSD ThermalShutdown 140°C

TSD_HYS ThermalShutdownHysteresis 15

VCT_DIS Charge Timer Disable Threshold No timer if CT voltage is less thanVCT_DIS

0.4 V

1.Specificationoverthe–25°Cto+85°Coperatingtemperaturerangeisassuredbydesign,characterizationandcorrelationwithstatisticalprocesscontrols.

AAT3620 DATA SHEET




Typical Characteristics

85°C25°C-25°C

Charging Current vs. Battery Voltage

Battery Voltage (V)

Cha

rgin

g C

urre

nt (m

A)

2.2 2.5 2.8 3.1 3.4 3.7 4.0 4.30

300

600

900

1200

1500

1800

2100

2400

Constant-Current Charge ModeCurrent vs. ISET Resistor

(VIN = 5V; VBAT = 3.5V)

ISET Resistor (kΩ)

Fast

Cha

rge

Cur

rent

(mA

) 22502000

1750

15001250

1000750

500250

010010 30 50 70 90

Termination Current vs. Temperature (VIN = 5V; RTERM = 49.9KΩ)

Temperature (°C)

Term

inat

ion

Cur

rent

(mA

)

-40 -15 10 35 60 8540424446485052545658606264

Recharge Voltage vs. Temperature (VIN = 5V)

Temperature (°C)

End

of C

harg

e Vo

ltage

(V)

-40 -15 10 35 60 854.050

4.055

4.060

4.065

4.070

4.075

4.080

Preconditioning Rising Threshold Voltagevs. Temperature

(VIN = 5.5V)

Temperature (°C)

Prec

ondi

tioni

ng R

isin

gTh

resh

old

Volta

ge (V

)

-40 -15 10 35 60 852.56

2.57

2.58

2.59

2.60

2.61

2.62

2.63

2.64

Shutdown Current vs. Input Voltage

4.5 5.0 5.5 6.0

Input Voltage (V)

Shut

dow

n C

urre

nt (µ

A)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-25°C25°C85°C

AAT3620 DATA SHEET




Typical Characteristics

Charge Current vs. Input Voltage (T = -25°C)

Input Voltage (V)

Bat

tery

Cha

rgin

g C

urre

nt (m

A)

4.0 4.4 4.8 5.2 5.6 6.04.2 4.6 5.0 5.4 5.80

300

600

900

1200

1500

1800

2100

2400

VBAT = 2.7VVBAT = 3.3V VBAT = 3.6V VBAT = 3.9V

Charge Current vs. Input Voltage (T = 85°C)

Input Voltage (V)

Cha

rge

Cur

rent

(mA

)

4.0 4.5 5.0 5.5 6.0 6.50

500

1000

1500

2000

2500

VBAT = 2.7VVBAT = 3.3V VBAT = 3.6V VBAT = 3.9V

AAT3620 DATA SHEET




Functional Description

Control LoopThe AAT3620 uses an average current mode step-down converter to implement the DC/DC switch-mode con-verter function during constant current mode charging. The technique of average current mode control over-comes peak current control problems by introducing a high gain integrating current error amplifier into the cur-rent loop. Average current tracks the sensed output cur-rent with a high degree of accuracy and the noise immu-nity is excellent. The oscillator saw-tooth ramp provides compensation so no slope compensation is required for dutycycleexceeding50%.Thehighgainofthecurrenterror amplifier at DC accurately programs the output. The switching charger works in continuous current mode PWM only. There is a soft start before entering constant current charging mode and the charger re-enters linear operation in constant voltage mode when the charge current drops below 300mA.

Linear vs. Switching Battery ChargingThe AAT3620 performs battery charging using the ben-efits of the step-down or "buck" architecture to multiply the input current when stepping down the output volt-age. This property is expressed mathematically in the comparison below, and provides the ability to maximize battery charging from current limited devices, as well as greatly decrease power and heat related dissipation.

Linear ChargingLinear charge current relationship1:

IBATL = IIN

Efficiency of linear charger:

η = VBAT

VIN

Functional Block Diagram

PWM / Linear Charge Control

Reverse Blocking

VPIN

VCC

EN

BAT

ISET

Over-TemperatureProtection

LX

CS

Charge status

TS

Current Set

GND

STAT2TimerCT

PGND

Reverse Blocking

TERM

VREF

STAT1

Volt Det/UVLO

1. Equation does not take into account thermal foldback.

AAT3620 DATA SHEET




Switch-Mode ChargingSwitch-modecurrentrelationship:

IBATS = ηS · VIN · IIN

VBAT

WhereηS=90%.

Example: Power SavingsConventional Linear Charger IC:

PD = (VIN - VBAT) ∙IBAT = (5 - 3.5) ∙ 0.5 = 0.75W

Switch-ModeChargerIC:

η VBAT ∙ IBATPD = - VBAT ∙ IBAT = - 3.5 ∙ 0.5 = 0.195W3.5 ∙ 0.5

0.9

Adapter Input Charge Inhibit and ResumeTheAAT3620hasaUVLOandpoweronresetfeaturesothat if the input supply to the ADP pin drops below the UVLOthreshold,thechargerwillsuspendchargingandshut down. When power is re-applied to the IN pin or the UVLOconditionrecovers,thesystemchargecontrolwillassess the state of charge on the battery cell and will automatically resume charging in the appropriate mode for the condition of the battery.

Input/Output Capacitor and InductorThe AAT3620 contains a high performance 2A, 1.5MHz synchronous step-down converter. The step-down con-verter operates to ensure high efficiency performance over all load conditions. It requires only 3 external power components (CIN, COUT, and L).

Apart from the input capacitor, only a small L-C filter is required at the output side for the step-down converter to operate properly. Typically, a 4.7µH inductor such as theWurth7447789004anda22µFto47µFceramicout-put capacitor is recommended for low output voltage ripple and small component size. Ceramic capacitors with X5R or X7R dielectrics are highly recommendedbecauseoftheirlowESRandsmalltemperaturecoeffi-cients. A 10μF ceramic input capacitor is sufficient formost applications.

Battery ChargingBattery charging starts only after the AAT3620 checks several conditions in order to maintain a safe charging

environment. The input supply must be above the mini-mumoperating voltage (UVLO) and above the batteryvoltageby0.3V,thebatterytemperaturemustbewithinthe0°C~45°Crange,andtheenablepinmustbehigh.The AAT3620 checks the condition of the battery and determines which charging mode to apply. If the battery voltage is below VBAT_BC, the AAT3620 begins battery conditioning until the battery voltage reaches VBAT_BC. Thebatteryconditioningcurrentis10%ofconstantcur-rent level.OncetheAAT3620reachesVBAT_BC, it begins constant current mode charging. The constant current mode current level is programmed using a single resistor fromtheISETpintoground.Programmedcurrentcanbe set from a minimum of 1A to a maximum of 2.0A. Constant current charging will continue until the battery voltage reaches the voltage regulation point VBAT_REG. WhenthebatteryvoltagereachesVBAT_REG, the AAT3620 will transition to constant-voltage mode. The regulation voltage is factory programmed to a nominal 4.2V andwill continue charging until the charging current has reduced to the termination current programmed by the resistorconnectedfromITERMtoground.Thetermina-tion current program range is from 50mA to 200mA. After the charge cycle is complete, the AAT3620, turns off the series pass device and automatically goes into a power saving mode. During this time the series pass device will block current in both directions therefore pre-venting the battery from discharging through the IC.

The AAT3620 will shutdown if the charger source is dis-connected until the charging source is reconnected and VINisgreaterthantheVIN_SLEEP threshold.

Figure 1 illustrates the entire battery charging profile, which consists of three phases.

1. Preconditioning-Current Mode (Trickle) Charge2. Constant-Current Mode Charge3. Constant-VoltageModeCharge

Thebatterypreconditioningcurrent isequal to10%ofthe constant current charging level, so the battery pre-conditioning current range is 100mA to 200mA. Linear mode is on standby while switch-mode is active in the constantcurrentchargingregion2.6V<VBAT<4.2V.Thecharger will re-enter linear mode while in constant volt-age mode after the switch-mode current drops below 300mA. The termination current is programmed by an externalresistorwithaseparateITERMpinandtheter-mination current set pin also monitors the charge cur-rent. The output short circuit current is equal to the bat-tery preconditioning current.

AAT3620 DATA SHEET




Preconditioning Trickle ChargeBattery charging commences only after the AAT3620 battery charger checks several conditions in order to maintain a safe charging environment. The Systemoperation flow chart for the battery charger operation is shown in Figure 2. The input supply must be above the minimumoperatingvoltage(UVLO)andtheenablepin(EN) must be high (it is internally pulled up). When the battery is connected to the BAT pin, the battery charger checks the condition of the battery and determines which charging mode to apply.

Preconditioning-Current Mode Charge CurrentIf the battery voltage is below the Preconditioning Voltage Threshold VCH_BC, the battery charger initiates precondition trickle charge mode and charges the bat-teryat10%oftheprogrammedconstant-currentmag-nitude. For example, if the programmed current is 1A, the trickle charge current will be 100mA. Trickle charge is a safety precaution for a deeply discharged cell. It also reduces the power dissipation in the internal series pass MOSFETwhentheinput-outputvoltagedifferentialisatits highest.

Constant-Current Mode Charge CurrentTrickle charge continues until the battery voltage reach-esVBAT_BC. At this point the battery charger begins con-stant-current charging. The current level default for this modeisprogrammedusingaresistorfromtheISETpinto ground. Programmed current can be set at a mini-mum of 100mA and up to a maximum of 2.0A.

The AAT3620 contains a high performance 2A, 1.5MHz synchronous step-down converter. The step-down con-verter operates to ensure high efficiency performance over all load conditions. It requires only 3 external power components (CIN, COUT, and L).

Constant-Voltage Mode ChargeConstant current charging will continue until the battery voltage reaches the Output charge voltage regulationpointVBAT_REG.WhenthebatteryvoltagereachesVBAT_REG, the battery charger transitions to constant-voltage mode.VBAT_REGisfactoryprogrammedto4.2V(nominal).Charging in constant-voltage mode will continue until the charge current has reduced to the programmed end of charge termination current.

Constant CurrentFast Charge Phase

PreconditioningTrickle ChargePhase

Charge Complete Regulated Voltage

4.2

Constant Current Mode Voltage

Threshold2.6

Regulated Current1C

Trickle Charge andTermination Threshold(Programmable)

Battery Recharge Voltage Threshold

Battery DischargeConstant VoltageTaper Charge Phase

Constant VoltageTaper Charge Phase

V I

300

Time

mA

L S L S L

Charge PhaseConstant Current

1 2 3 2 3

Figure 1: Charging Current and Battery Voltage vs Time.

The profile consists of three phases: 1. Preconditioning-Current Mode (Trickle) Charge - Linear Mode 2.Constant-Current(Fast)ModeCharge-SwitchingMode 3.Constant-VoltageMode(Taper)Charge-Switching/LinearMode.

AAT3620 DATA SHEET




System Operation Flowchart

Power On Reset

PowerInput Voltage VCC > VCC_UVLO

FaultConditions Monitoring

OV, OT, VTS1 < TS < VTS2

Preconditioning Test

VBAT < VBAT_BC

VBAT > VBAT_BC

Current Phase TestVBAT < VBAT_REG

VBAT > VBAT_REG

Voltage Phase TestIBAT > ICH_TERM

IBAT < ICH_TERM

No

No

Yes

No

Preconditioning (Trickle Charge)

Constant Current Charge

Mode

Constant Voltage Charge

Mode

Yes

Yes

Yes

Charge Completed

Charge Timer Control

No

Recharge Test VBAT> VBAT_RCH

Yes

No

Shut Down Yes

Enable

YesNo

No

Expired

Figure 2: System Operation Flowchart for the Battery Charger.

AAT3620 DATA SHEET




Power Saving ModeAfter the charge cycle is complete, the battery charger turns off the series pass device and automatically goes into a power saving mode. During this time, the series pass device will block current in both directions to pre-vent the battery from discharging through the battery charger.Onlyinpowersavemodewillthebatterychar-ger monitor all parameters and resume charging in the most appropriate mode.

Sleep ModeThe battery charger will shutdown if the charger source isdisconnectedandVINislessthanVIN_SLEEP threshold. It willcomeoutofsleepmodeifeitherVIN is greater than VIN_SLEEPorENpiniscycledhighwhileVIN is greater than VIN_SLEEP.

Programming Charge Current (ISET)The default constant current mode charge level is user programmedwithasetresistorplacedbetweentheISETpin and ground. The accuracy of the constant charge cur-rent, as well as the preconditioning trickle charge cur-rent, is dominated by the tolerance of the set resistor. For thisreason,a1%tolerancemetalfilmresistorisrecom-mended for the set resistor function. The constant charge current levels from 1A to 2A may be set by selecting the appropriate resistor value from Table 1.

RSET (kΩ) ICH_CC (mA)100 200090 180080 160070 140060 120050 100040 80030 60020 400

Table 1: ISET Resistor vs. Constant Charge Current Mode Current.

Programmable Charge Termination CurrentThe charge termination current ICH_TERM can be pro-grammedbyconnectingaresistorfromTERMtoGND:

ICH_TERM = · 10-6RTERM

IftheTERMpinisleftopen,theterminationcurrentlevelwill be set to 200mA as the default value.

When the charge current drops to the termination cur-rent level, the device terminates charging and goes into a power-save mode. The charger will remain in this mode until the battery voltage decreases to a level below thebatteryrechargevoltagethreshold(VBAT_RCH).

Consuming very low current in the power-save mode, the AAT3620 minimizes battery drain when it is not charging. This feature is particularly useful in applica-tions where the input supply level may fall below the battery charge. If the AAT3620 input voltage drops, the device will enter sleep mode and automatically resume charging once the input supply has recovered from the fault condition.

The TERM pin can also be used as a charge currentmonitor based on the following equation:

Charge Current Voltage Level = 1A/V

AAT3620 DATA SHEET




The LEDs should be biased with as little current as nec-essary to create reasonable illumination; therefore, aballast resistor should be placed between the LED cath-odeandtheSTATpins.LEDcurrentconsumptionwilladdto the overall thermal power budget for the device pack-age, hence it is good to keep the LED drive current to a minimum. 2mA should be sufficient to drive most low cost green or red LEDs. It is not recommended to exceed 8mA for driving an individual status LED. The required ballast resistor values can be estimated using the follow-ing formula:

VIN - VF(LED)RBALLAST = ILED

Example:5.0V - 2.0VRBALLAST = = 1.5kW2mA

Note:RedLEDforwardvoltage(VF) istypically2.0V@2mA.

Protection Circuitry

Charge Safety Timer (CT)While monitoring the charge cycle, the AAT3620 utilizes a charge safety timer to help identify damaged cells and toensurethatthecellischargedsafely.Operationisasfollows: upon initiating a charging cycle, the AAT3620 charges thecellat10%of theprogrammedmaximum

chargeuntilVBAT>2.6V. If thecellvoltage falls to theprecondition threshold of 2.6V (typ) before the safetytimer expires, the cell is assumed to be damaged and the charge cycle terminates. If the cell voltage exceeds 2.6Vpriortotheexpirationofthetimer,thechargecycleproceeds into fast charge. Three timeout periods of 25 minutes for Trickle Charge mode, 2.2 hours for Constant Current Mode including Trickle Charge and 3 hours for ConstantVoltagemode.

Mode TimeTrickleCharge(TC)TimeOut 25 minutes

Trickle Charge (TC) + Constant Current (CC)ModeTimeOut 2.2 hours

ConstantVoltage(CV)ModeTimeOut 3 hours

Table 3: Summary for a 0.1µF Ceramic Capacitor Used for the Timing Capacitor.

The AAT3620 has a battery fault detector, which, when usedinconjunctionwitha0.1μFcapacitorontheCTpin,outputsa1Hzsignalwith50%dutycycleattheSTAT1pin in the event of a timeout while in the trickle charge mode.

The CT pin is driven by a constant current source and will provide a linear response to increases in the timing capacitor value. Thus, if the timing capacitor were to be doubledfromthenominal0.1μFvalue,thetime-outperi-ods would be doubled. If the programmable watchdog timer function is not needed, it can be disabled by termi-natingtheCTpintogroundorVCConlyforAAT3620-2.

Status Indicator (STAT1/2)

Charge Status OutputTheAAT3620providesbatterychargestatusviatwostatuspins(STAT1andSTAT2).EachofthetwopinsisinternallyconnectedtoanN-channelopendrainMOSFET.Thestatuspincanindicatethefollowingconditions:

Conditions STAT1 STAT2Pre-Charge ON ONFast-Charge ON OFF

End of Charge (Charge Complete) OFF ONCharge Disabled OFF OFF

SleepMode(VIN <VIN_SLEEP) OFF OFFNo battery with Charge Enabled - AAT3620 (No

BAT Detect) FLASH

50%DutyCycleFLASH

50%DutyCycleNo battery with Charge Enabled - AAT3620-2 (No

BAT Detect and safety timer disabled)FLASH

RatedependsonoutputcapacitanceFLASH

RatedependsonoutputcapacitanceFaultCondition(Battery0V) OFF OFF

FaultCondition(BatteryOT/UT) OFF OFFFaultCondition(DeviceOT) OFF OFF

Fault(TimeOut) OFF OFF

Table 2: LED Status Indicator STAT1 and STAT2.

AAT3620 DATA SHEET




Note that disabling the safety timer (CT pin grounded) on theAAT3620will lead to false "NOBAT"detectionandbothSTATpinswillgolow.

The CT pin should not be left floating or unterminated, as this will cause errors in the internal timing control circuit. The constant current provided to charge the timing capacitor is very small, and this pin is susceptible to noise and changes in capacitance value. Therefore, the timing capacitor should be physically located on the printed circuit board layout as close as possible to the CT pin.Sincetheaccuracyoftheinternaltimerisdominatedby the capacitance value, a 10% tolerance or betterceramic capacitor is recommended. Ceramic capacitor materials,suchasX7RandX5Rtypes,areagoodchoicefor this application.

The AAT3620 has the no-battery detection function, "No-BAT". The CT pin capacitor (CCT) sets up an internal clock to reset the no-battery detector every 8 clock peri-ods. The internal clock frequency is inversely propor-tional to the CCT:

f = 100nF ∙ Hz

CCT

The no-battery detection function works by detecting the charger toggling between charge termination and the recharge threshold more than 4 times every 8 clock periods. In the event the battery is disconnected while powered on, the recommended 0.1µF capacitor at CT pin createsa1HzinternalclocktomaketheSTATLEDblinkat 1Hz, 50% duty cycle, to indicate "no battery con-nected". To ensure that the charger cycles between charge termination and recharge more than 4 times in 8 seconds, the BAT pin capacitor cannot exceed 22µF for every 100nF on the CT pin. For example, if CCT is 220nF, the capacitor on the BAT pin cannot exceed 47µF. If more capacitance is used on the BAT pin, it will take longer than 8 clock periods to complete 4 charge termi-nation/recharge cycles and the no-battery detection will not work.

Over-Voltage ProtectionAn over-voltage event is defined as a condition where the voltage on the BAT pin exceeds the maximum battery charge voltage and is set by the over-voltage protection threshold(VBAT_OVP). If an over-voltage condition occurs, the AAT3620 charge control will shut down the device untilthevoltageontheBATpindropsbelowVBAT_OVP. The AAT3620 will resume normal charging operation after the over-voltage condition is removed. During an over-volt-ageevent,theSTATLEDswillreportasystemfault.

Over-Temperature ShutdownThe AAT3620 has a thermal protection control circuit which will shut down charging functions should the inter-nal die temperature exceed the preset thermal limit threshold.Oncetheinternaldietemperaturefallsbelowthe thermal limit, normal operation will resume the pre-vious charging state.

Battery Temperature Fault Monitoring (TS)In the event of a battery over-temperature condition, the charge control will turn off the internal pass device and report a battery temperature fault on the STAT pins.After the system recovers from a temperature fault, the device will resume charging operation. The AAT3620 checks battery temperature before starting the charge cycle, as well as during all stages of charging. This is accomplishedbymonitoring the voltageat theTSpin.The internal battery temperature sensing system (Figure 4) is comprised of two comparators which establish a voltage window for safe operation. The thresholds for the TSoperatingwindowareboundedby theVTS1andVTS2 specifications. Referring to the electrical characteristicstableinthisdatasheet,theVTS1threshold=0.30·VCC

andtheVTS2threshold=0.60·VCC.

This system is intended for use with negative tempera-ture coefficient thermistors (NTC) which are typically integrated into the battery package. Most of the com-monly used NTC thermistors in battery packs are approximately10kΩatroomtemperature(25°C).Ifthebattery becomes too hot during charging due to an internal fault or excessive constant charge current, the thermistor will heat up and reduce in value, pulling the TS pin voltage lower than the TS1 threshold, and theAAT3620 will stop charging until the condition is removed, when charging will be resumed.

Inorder to accurately set theTSvoltageaccording tothe temperature coefficient and the nominal value of the thermistor, two resistors may be used as shown in the example below. It is recommended to use NTC thermis-torsinthe10Kto100KOhmrange,withBetaconstantvalues in the 3000 to 5000 range.

RT2 = (Ω)

RT1 =

RNTC(HOT) ∙ RNTC(COLD) ∙ - 1 1

Ratio Cold Ratio Hot

RNTC(HOT) ∙ - 1 - 1Ratio Hot

RNTC(COLD) ∙ - 11

Ratio Cold

RT2 ∙ RNTC(COLD) Ratio Cold RT2 + RNTC(COLD)

1 - Ratio Cold - (Ω)

AAT3620 DATA SHEET




Where:

Ratio(Cold)=0.60(2%tolerance)

Ratio(Hot)=0.30(2%tolerance)

RNTC(COLD) = Thermistor resistance at Cold (typically 0°C)

RNTC(HOT) = Thermistor resistance at Hot (Typically 45°C)

Fora10kΩNTCthermistorwithaBetaof3370:

RNTC(0°C)=28.1kΩ

RNTC(45°C)=4.91kΩ

And the calculation results are as follows:

RT2=31.6kΩ

RT1=9.92kΩ

IftheuseoftheTSpinfunctionisnotrequiredbythesystem,itshouldbetiedtoVCCusinga10kΩresistor.

0.60 ∙ VCC

Battery Cold Fault

Battery Hot Fault

VCC

TS

Pack

0.30 ∙ VCC

Battery

RT1

RT2

RNTC

VCC

Figure 3: AAT3620 Battery Temperature Sense Circuit.

Thermal ConsiderationsThe actual maximum charging current is a function of Charge Adapter input voltage, the state of charge of the battery at the moment of charge, the system supply cur-rent from the BAT pin, the ambient temperature and the thermal impedance of the package. The maximum pro-grammable current may not be achievable under all operating parameters.

The AAT3620 is offered in a TDFN33-14 package which can provide up to 2W of power dissipation when it is

properly bonded to a printed circuit board and has a maximum thermal resistance of 50°C/W. Many consider-ations should be taken into account when designing the printed circuit board layout, as well as the placement of the charger IC package in proximity to other heat gen-erating devices in a given application design. The ambi-ent temperature around the charger IC will also have an effect on the thermal limits of a battery charging applica-tion. The maximum limits that can be expected for a given ambient condition can be estimated by the follow-ing discussion. First, the maximum power dissipation for a given situation should be calculated:

TJ(MAX) - TAPD(MAX) = θJA

Where:

PD(MAX) = Maximum Power Dissipation (W)θJA=PackageThermalResistance(°C/W)TJ(MAX)=MaximumDeviceThermalShutdownTemperature

(°C) [140°C]TA = Ambient Temperature (°C)

The power dissipation for both the linear charging mode and the switching charger mode should be considered.

The power dissipation for the switching charger can be calculated by the following equation:

PD(MAX) =

+ [(tSW · fSW · ICH_CC + IqOP) · VPIN]

TJ(MAX) = TA + qJA · PD(MAX)

ICH_CC2 · [RDSONHS · VBAT + RDSONLS · (VPIN - VBAT)]

VPIN

Where:

PD(MAX) = Total Power Dissipation by the DeviceVPIN=AdapterInputVoltageVBAT=BatteryVoltageattheBATPinICH_CC = Constant Charge Current Programmed for the

ApplicationIQOP = Quiescent Current Consumed by the IC for Normal Operation[5mA]

RDS(ON)HSandRDS(ON)LS=On-resistanceofstep-downhighandlowsideMOSFETs

The power dissipation for the linear charging mode can be calculated by the following equation:

PD(MAX) = (VPIN - VBAT) · ICH_BC + VPIN · IQOP

Where:

PD(MAX) = Total Power Dissipation by the Device

AAT3620 DATA SHEET




VPIN=InputVoltageVBAT=BatteryVoltageasSeenattheBATPinICH_BC = Battery Conditioning Charge Current Programmed

for the ApplicationIQOP = Quiescent Current Consumed by the Charger IC forNormalOperation[5mA]

By substitution, we can derive the maximum charge cur-rent before reaching the thermal limit condition (thermal loop). The maximum charge current is the key factor when designing battery charger applications.

PD(MAX) - VPIN · IQOP

VPIN - VBATICH_BC(MAX) =

TJ - TA

θJA VIN - VBAT

ICH(MAX) =- VPIN · IQOP

In general, the worst condition is the greatest voltage drop across the charger IC, when battery voltage is charged up to the preconditioning voltage threshold and entering Constant Current switching charge mode.

Example Worst Case Power DissipationThe worst case power dissipation can be calculated using the lowest battery voltage level when the charger enters CC charge mode and the charge current is set to 2A.

ICH_CC = 2AVPIN=6VRDSONHS=0.3ΩRDSONLS=0.25ΩtSW = 5 · 10-9IQOP = 0.005AfSW = 1.5 · 106

TA = 85°CθJA = 50°C/W

PD(MAX) =(2A)2 · [0.3Ω · 2.8V + 0.25Ω · (6V - 2.8V)]

6V+ [(5 · 10-9 · [1.5 · 106]· 2A + 0.005A) · 6V]

PD(MAX) = 1.213W

TJ(MAX) = 85 + 50 · 1.213

TJ(MAX) = 145.65

For the Linear Mode:

IQOP = 0.005AVPIN=6VVBAT=2VICH_BC = 0.2A

PD(MAX) = (6V - 2V) · 0.2A + 6V · 0.005A

PD(MAX) = 0.83W

PCB Layout GuidanceFigure 4 is the evaluation board schematic. The evalua-tion board has additional components for easy evalua-tion;theactualbillofmaterialsrequiredforthesystemis shown in Table4.

When laying out the PC board, follow the guidelines below to ensure proper operation of the AAT3620:

1. SoldertheexposedpadEPreliablytoPGND/AGNDand multilayer GND. Connect the exposed thermal pad should to board ground plane and pins 2 and 3. Include a large exposed copper pad under the pack-age in the ground plane with vias to all board layers for thermal dissipation.

2. Keep the power traces, including GND traces, the LX tracesand theVIN trace short, direct andwide toallow large current flow. Make the L1 connection to the LX pins as short as possible. Use several viapads when routing between layers.

3. Connect the input capacitors (C1, C4, and C5) as close as possible to VPIN (Pin 1) VCC (Pin 4) andGND/PGND (Pin 2,3) to get good power filtering.

4. Connect the output capacitors C2 and C7 and induc-tor L1 as close as possible and do not route any signal lines under the inductor.

5. Keep the resistance of the trace from the load return to the PGND (Pin 2) to a minimum. This will help to minimize any error in DC regulation due to differ-ences in the potential of the internal signal ground and the power ground.

AAT3620 DATA SHEET




BATGNDTS

TB1

VPIN1

PGND2

GND3

VCC4

EN5

ISET6

CT7 STAT2 8

BAT 12

STAT1 9

TERM 10

TS 11

CS 13

LX 14

EP

AAT3620-TDFN33-14

U1

4.7µHL1

EN

JP1

STAT1

D1

STAT2

D2

100kΩ

R4 49.9kΩ

R3

10kΩR1

10kΩR2

VCC

TSJP2

0.1µFC3

2kΩR5

2kΩ

R6

VIN

0.1µFC1

1µFC5

VIN

TB2GND

10µFC4

TS

TP7

GNDTP6

VINTP1

CSTP5

LX

TP4

BATTP8

VCC

TP2100Ω

R7

GNDTP3

22µF

C2

0.1µF

C7

0.1µFC6

Figure 4: AAT3620 2A Evaluation Board Schematic.

Quantity Value Designator Footprint Description1 10µF C4 0805 Capacitor,Ceramic,X5R,10V,±20%4 0.1µF C1, C3, C6, C7 0603

Capacitor,Ceramic,20%,10V,X5R1 22µF C2 12061 1µF C5 06031 4.7µH L1 7mm x 7mm Inductor,Wurth,74477890042 10K R1,R2 0402

Resistor,5%2 2k R5,R6 04021 49.9k R3 0402

Resistor,1%1 100k R4 04021 100 R7 04022 LED D1, D2 0402 RedandGreenSMD

Table 4: Minimum AAT3620 Bill of Materials.

AAT3620 DATA SHEET




(a) Top Layer (b) Bottom Layer

Figure 5: AAT3620 Evaluation Board.

AAT3620 DATA SHEET




Ordering Information

Package Part Marking1 Part Number (Tape and Reel)2

TDFN33-14 6WXYY AAT3620IWO-4.2-T1TDFN33-14 X7XYY AAT3620IWO-4.2-2-T1

Skyworks Green™ products are compliant with all applicable legislation and are halogen-free.For additional information, refer to Skyworks Definition of Green™, document number SQ04-0074.

Packaging Information

TDFN33-143

Top View Bottom View

3.000 ± 0.050

Index Area

3.00

0 ±

0.05

0

Detail "A"

1.650 ± 0.050

2.50

0 ±

0.05

0

0.20

3 R

EF

0.75

0 ±

0.05

0

0.000 + 0.100- 0.000

Detail "A"

Side View

0.425 ± 0.050

0.40

0 B

SC

0.18

0 ±

0.05

0

Pin 1 Indicator(Optional)

All dimensions in millimeters.

1.XYY=assemblyanddatecode.2.SamplestockisgenerallyheldonpartnumberslistedinBOLD.3.Theleadlesspackagefamily,whichincludesQFN,TQFN,DFN,TDFNandSTDFN,hasexposedcopper(unplated)attheendoftheleadterminalsduetothemanufacturing

process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.

AAT3620 DATA SHEET




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